At BRS, every order ships free using a mix of economy shipping methods including, USPS, SurePost and UPS Ground. Your order will arrive within 2-7 days, depending on your vicinity to Minneapolis. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous USA. Frozen foods and post office boxes do not qualify for free shipping.*

$4.99 Upgraded 1-3 Day Shipping (Free over $249)

Your order will be upgraded from economy methods to ensure 1-3 business day delivery using UPS 3 day select and UPS ground regardless of weight or size. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous USA. Frozen foods and post office boxes do not qualify for upgraded shipping. See map below for transit times.*

*Click here to view detailed shipping information.
* Orders shipped same day when placed by 3:30pm CST, Monday through Friday. Orders placed after will ship the following business day. Example: order after 3:30pm CST on Monday, it will ship Tuesday. Order after 3:30pm CST on Friday, it will ship Monday.

At BRS, every order ships free using a mix of economy shipping methods including, USPS, SurePost and UPS Ground. Your order will arrive within 2-7 days, depending on your vicinity to Minneapolis. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous USA. Frozen foods and post office boxes do not qualify for free shipping.*

$4.99 Upgraded 1-3 Day Shipping (Free over $249)

Your order will be upgraded from economy methods to ensure 1-3 business day delivery using UPS 3 day select and UPS ground regardless of weight or size. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous USA. Frozen foods and post office boxes do not qualify for upgraded shipping. See map below for transit times.*

*Click here to view detailed shipping information.
* Orders shipped same day when placed by 3:30pm CST, Monday through Friday. Orders placed after will ship the following business day. Example: order after 3:30pm CST on Monday, it will ship Tuesday. Order after 3:30pm CST on Friday, it will ship Monday.

Ships Monday

Free economy shipping on every order!

At BRS, every order ships free using a mix of economy shipping methods including, USPS, SurePost and UPS Ground. Your order will arrive within 2-7 days, depending on your vicinity to Minneapolis. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous USA. Frozen foods and post office boxes do not qualify for free shipping.*

$4.99 Upgraded 1-3 Day Shipping (Free over $249)

Your order will be upgraded from economy methods to ensure 1-3 business day delivery using UPS 3 day select and UPS ground regardless of weight or size. Place your order by 3:30 PM CST Monday through Friday and we'll ship it the same day. This offer is only available to the contiguous USA. Frozen foods and post office boxes do not qualify for upgraded shipping. See map below for transit times.*

*Click here to view detailed shipping information.
* Orders shipped same day when placed by 3:30pm CST, Monday through Friday. Orders placed after will ship the following business day. Example: order after 3:30pm CST on Monday, it will ship Tuesday. Order after 3:30pm CST on Friday, it will ship Monday.

Quick Overview

The Tunze Osmolator Nano 3152 Auto Top Off is designed for smaller tanks, approximately 50 gallons and under. One of the safest ATO’s available. Utilizes an single sensor to monitor water levels and a controller that protects against overdosing.

Excellent productBy Richie Don 11/4/2016

Richie D would recommend this product to a friend

Sure is convenient not having to add to-off water all the time. Just went away for the weekend and didn't have to worry about whether or not the gravity fed system I had always used would work or not. Many times I would come home to find the pump sucking air and the aquarium down about 4 inches. Not this time! While it is very expensive, it does save a lot of headaches and potential loss of fish and corals. Absolutely recommend it.

Great mini version of the bigger atoBy Sgt Haroldon 9/13/2016

Sgt Harold would recommend this product to a friend

I brought this for my Red Sea max 250 rimless . It has a small tank that I use a 5 gal bucket to keep full. Keeping salinity if important in maintaining a stably ecosystem .

Part #4017.000 Controller Osmolator nano deviceBy Maxon 8/3/2016

Max wouldn't recommend this product to a friend

I have written to the company in Germany to try to get a new part #4017.000 Controller Osmolator Nano device. I have to unplug the device and reconnect it every cpl days to get the unit to work properly to top off. It makes a noise like it wants to pump water to my reef tank but will not until I unplug the device and re-connect it then it works for a day or two. I hope I can get a replacement part as I only bought this from BRS beginning of July last month. I sent the scan of my invoice to the company in Germany as well so waiting on a response.

GreatBy darryl heyon 8/1/2016

darryl hey wouldn't recommend this product to a friend

have 3 of these on nano tanks 29 biocube 40 breader and 45 cube works great! have been running for 2 years now

Auto shut offBy Chrison 7/2/2016

Chris wouldn't recommend this product to a friend

The float sensor got stuck on and the pump did not turn off. The auto turn off did not work. Luckily the story revisor was almost empty and my tank did not overflow. I don't trust it any more need to upgrade to the one with the optical sensor.

Great nano ATOBy Tommyon 6/13/2016

Tommy would recommend this product to a friend

I installed the Tunze nano ATO in my Corallife Biocube 29. I placed it in the 3rd chamber with the return pump. So far it works perfectly. It has helped stabilize the tank and my corals could not be happier. Great little ATO.

Had defective pumpBy Mikeon 4/25/2016

Mike would recommend this product to a friend

My experience is mix. The product works well for 10 days then stopped. Tunze customer service replace the pump and is wrking fine now. Just the trouble of not wrking and having to contact Tunze for replace part.

Works great! By Rachelleon 2/15/2016

Rachelle would recommend this product to a friend

This is a very nice ATO system, it works like a charm and keeps my salinity nice and stable. My only complaint is that it doesn't have a way to keep the pump sitting flat.

AmazingBy Jackon 1/14/2016

Jack would recommend this product to a friend

i have been looking for an ato for a while, and i found tunze's products. i didnt really want to spennd $200 on the osmolator, so i tried the nano osmolator. works great, and has an auto shut off just in case it fails. another quality product by tunze

Terrible By Brandonon 8/31/2015

Brandon wouldn't recommend this product to a friend

The reason why the normal tunze osmolator does so well and sells so often is because the eye sensor it has well in this Nano version there's none witch makes this just as good as a lowest model auto top off u can buy for a few dollers or even make not worth it and don't use it trust me

Great Nano ATOBy Sterlingon 7/23/2015

Sterling would recommend this product to a friend

This is an excellent ATO. I'm new to reefing and everywhere I read ATO's were on top of the suggestion list. I bought this with everything else to setup my new tank and I'm very glad I did. It was easy to setup, works as advertised, and leaves a little footprint. Worth the price and it's one less thing I need to worry about.

Love this thingBy AdamNCon 6/29/2015

AdamNC would recommend this product to a friend

Been using it for a few months now with little issues. One issue is with the supplied hose the pump in the reservoir tends to sit sideways. But that's not fault of the actual equipment just the hose. And on a rimmed tank it does make the water line sit about 2-3mm below the rim. Nothing major just a peeve but I'm used to it now. It actually allows me to see that the water line is constant in the tank. Other then those two things I love it. Mechanically I've had no issues.

Product Questions

Hey brs,
What's the main differences between the nano and the 3155? Also, would be possible to upgrade in the future without having to buy the whole thing?

Thanks

Question by: Matt on Dec 16, 2013 4:29:00 AM

Hi Matt,
The nano osmolator is just a simple float switch and that is it. The 3155 has the dual level control with the optical eye for primary control and the float switch emergency backup. The 3155 offers superior redundancy.

It would not be possible to upgrade, they are entirely different units.

Hey guys, I've been thinking of adding an ATO to my 120gal reef. The price difference in the 3155 and 3152 is a factor. Does the 3152 nano also have a 10 minute internal shutoff timer? Or the ability to adjust the flow rate of the DC pump?
Thanks for the feedback.
Brad.

Question by: Brad on Jun 7, 2016 12:08:00 PM

Great question!
the Nano will have a 5 minute shut off and no ability to adjust he flow of the pump. In most cases this will be too limited for the 120 gallon. Feel free to let us know if you have any further questions!

I recently purchased one of these and think I will LOVE it but have a question. Each time I have gone to check on it, it seems the relay/sensor (whatever we call it) has shifted slightly so it is no longer sitting level. This is help on with the magnets, so am curious as to why this is happening or what I can do to stop it!

Question by: Wendy on May 18, 2015 12:54:00 PM

Great Question,
You can always try implementing a large magnet to ensure the hold is stronger. Other than that, there are some more permanent applications such as small amount of super glue. In any case your best bet will be to contact TUNZE and see if they have any tips or tricks.

I was curious if this auto top off will work for my Innovative Marine NUVO 10. Would the water get too salty by the time the ATO kicks on?

Question by: Trenton on Jul 7, 2016 12:21:00 PM

Hi Trenton,
That is a valid concern and if you are keeping SPS in the 10 gallon then we would suggest looking into the Osmolator 3155, however for most fish, and other corals like softies and LPS the Osmolator nano will work just fine. Since the return pump compartment is much smaller than larger tanks, when water evaporates it will move the water level pretty quickly and activate the float switch which is pretty sensitive.

Hi Clayton,
The unit is not suited to large aquariums because it has a timer based cut off so the pump will only run for a short period of time. Using it with a large tank can result in the the pump turning off before its finished replacing the evaporation.

Introducing the little brother to the Tunze Osmolator, one of the industry’s most trusted automatic water top-off device and BRS Recommended. Designed specifically for smaller aquariums, roughly 50 gallons and under, the Osmolator Nano 3152 is a slimmed down version of the full sized 3155. It includes a processor-based anti-overfill system which turns the pump off if after five minutes of filling the level has still not been reached. The Osmolator Nano includes the control unit, low voltage (6V) pump, power adapter, 3m hose, magnet mount and protective cover.

Ask a question

Product Questions

Hey brs,
What's the main differences between the nano and the 3155? Also, would be possible to upgrade in the future without having to buy the whole thing?

Thanks

Question by: Matt on Dec 16, 2013 4:29:00 AM

Hi Matt,
The nano osmolator is just a simple float switch and that is it. The 3155 has the dual level control with the optical eye for primary control and the float switch emergency backup. The 3155 offers superior redundancy.

It would not be possible to upgrade, they are entirely different units.

Hey guys, I've been thinking of adding an ATO to my 120gal reef. The price difference in the 3155 and 3152 is a factor. Does the 3152 nano also have a 10 minute internal shutoff timer? Or the ability to adjust the flow rate of the DC pump?
Thanks for the feedback.
Brad.

Question by: Brad on Jun 7, 2016 12:08:00 PM

Great question!
the Nano will have a 5 minute shut off and no ability to adjust he flow of the pump. In most cases this will be too limited for the 120 gallon. Feel free to let us know if you have any further questions!

I recently purchased one of these and think I will LOVE it but have a question. Each time I have gone to check on it, it seems the relay/sensor (whatever we call it) has shifted slightly so it is no longer sitting level. This is help on with the magnets, so am curious as to why this is happening or what I can do to stop it!

Question by: Wendy on May 18, 2015 12:54:00 PM

Great Question,
You can always try implementing a large magnet to ensure the hold is stronger. Other than that, there are some more permanent applications such as small amount of super glue. In any case your best bet will be to contact TUNZE and see if they have any tips or tricks.

I was curious if this auto top off will work for my Innovative Marine NUVO 10. Would the water get too salty by the time the ATO kicks on?

Question by: Trenton on Jul 7, 2016 12:21:00 PM

Hi Trenton,
That is a valid concern and if you are keeping SPS in the 10 gallon then we would suggest looking into the Osmolator 3155, however for most fish, and other corals like softies and LPS the Osmolator nano will work just fine. Since the return pump compartment is much smaller than larger tanks, when water evaporates it will move the water level pretty quickly and activate the float switch which is pretty sensitive.

Hi Clayton,
The unit is not suited to large aquariums because it has a timer based cut off so the pump will only run for a short period of time. Using it with a large tank can result in the the pump turning off before its finished replacing the evaporation.

Full Details

Introducing the little brother to the Tunze Osmolator, one of the industry’s most trusted automatic water top-off device and BRS Recommended. Designed specifically for smaller aquariums, roughly 50 gallons and under, the Osmolator Nano 3152 is a slimmed down version of the full sized 3155. It includes a processor-based anti-overfill system which turns the pump off if after five minutes of filling the level has still not been reached. The Osmolator Nano includes the control unit, low voltage (6V) pump, power adapter, 3m hose, magnet mount and protective cover.

Reviews

Excellent productBy Richie D on 11/4/2016

Richie D would recommend this product to a friend

Sure is convenient not having to add to-off water all the time. Just went away for the weekend and didn't have to worry about whether or not the gravity fed system I had always used would work or not. Many times I would come home to find the pump sucking air and the aquarium down about 4 inches. Not this time! While it is very expensive, it does save a lot of headaches and potential loss of fish and corals. Absolutely recommend it.

Great mini version of the bigger atoBy Sgt Harold on 9/13/2016

Sgt Harold would recommend this product to a friend

I brought this for my Red Sea max 250 rimless . It has a small tank that I use a 5 gal bucket to keep full. Keeping salinity if important in maintaining a stably ecosystem .

Part #4017.000 Controller Osmolator nano deviceBy Max on 8/3/2016

Max wouldn't recommend this product to a friend

I have written to the company in Germany to try to get a new part #4017.000 Controller Osmolator Nano device. I have to unplug the device and reconnect it every cpl days to get the unit to work properly to top off. It makes a noise like it wants to pump water to my reef tank but will not until I unplug the device and re-connect it then it works for a day or two. I hope I can get a replacement part as I only bought this from BRS beginning of July last month. I sent the scan of my invoice to the company in Germany as well so waiting on a response.

GreatBy darryl hey on 8/1/2016

darryl hey wouldn't recommend this product to a friend

have 3 of these on nano tanks 29 biocube 40 breader and 45 cube works great! have been running for 2 years now

Auto shut offBy Chris on 7/2/2016

Chris wouldn't recommend this product to a friend

The float sensor got stuck on and the pump did not turn off. The auto turn off did not work. Luckily the story revisor was almost empty and my tank did not overflow. I don't trust it any more need to upgrade to the one with the optical sensor.

Great nano ATOBy Tommy on 6/13/2016

Tommy would recommend this product to a friend

I installed the Tunze nano ATO in my Corallife Biocube 29. I placed it in the 3rd chamber with the return pump. So far it works perfectly. It has helped stabilize the tank and my corals could not be happier. Great little ATO.

Had defective pumpBy Mike on 4/25/2016

Mike would recommend this product to a friend

My experience is mix. The product works well for 10 days then stopped. Tunze customer service replace the pump and is wrking fine now. Just the trouble of not wrking and having to contact Tunze for replace part.

Works great! By Rachelle on 2/15/2016

Rachelle would recommend this product to a friend

This is a very nice ATO system, it works like a charm and keeps my salinity nice and stable. My only complaint is that it doesn't have a way to keep the pump sitting flat.

AmazingBy Jack on 1/14/2016

Jack would recommend this product to a friend

i have been looking for an ato for a while, and i found tunze's products. i didnt really want to spennd $200 on the osmolator, so i tried the nano osmolator. works great, and has an auto shut off just in case it fails. another quality product by tunze

Terrible By Brandon on 8/31/2015

Brandon wouldn't recommend this product to a friend

The reason why the normal tunze osmolator does so well and sells so often is because the eye sensor it has well in this Nano version there's none witch makes this just as good as a lowest model auto top off u can buy for a few dollers or even make not worth it and don't use it trust me

Great Nano ATOBy Sterling on 7/23/2015

Sterling would recommend this product to a friend

This is an excellent ATO. I'm new to reefing and everywhere I read ATO's were on top of the suggestion list. I bought this with everything else to setup my new tank and I'm very glad I did. It was easy to setup, works as advertised, and leaves a little footprint. Worth the price and it's one less thing I need to worry about.

Love this thingBy AdamNC on 6/29/2015

AdamNC would recommend this product to a friend

Been using it for a few months now with little issues. One issue is with the supplied hose the pump in the reservoir tends to sit sideways. But that's not fault of the actual equipment just the hose. And on a rimmed tank it does make the water line sit about 2-3mm below the rim. Nothing major just a peeve but I'm used to it now. It actually allows me to see that the water line is constant in the tank. Other then those two things I love it. Mechanically I've had no issues.

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